Plastic nut with metallic thread engaging inserts



1966 T. E. FIDDLER 3, 86,578

PLASTIC NUT WITH METALLIC THREAD ENGAGING INSERTS Original F'iled Nov. 4, 1964 47 424,4 My; has...

CA TTQRMQY United States Patent r 2 Claims. (Cl. 8536) This application is a division of my copending application Serial No. 408,995, filed November 4, 1964, and relates to fasteners and, in particular, to molded nut bodies made of synthetic resin or plastic material and having metal insert thread members, and to attaching means such as bolts, studs, and cross-heads suitable for use with the novel nuts.

The devices of the invention provide fastening and attaching means which are not subject to the usual causes of decomposition such as rusting, oxidation, and electrolysis in the presence of moisture, salts and acids. The devices themselves constitute insulating members relative to metal items which they inter-connect especially were electrolysis is a factor in the decomposition of the metal parts, the fastening means, and the attaching means.

The mounting of metal trim moldings to metal panels in automobiles, appliances, and other items in a suitable example of an environment illustrating the utility of the invention. In such assemblies, the panel on which the molding is mounted may be ferrous metal and it may be suitable protectively and decoratively coated. The molding may be ferrous metal, white metal, stainless steel, aluminum, etc. The molding may be plated with nickel, chromium, etc. In the prior art, the studs or bolts may he ferrous, white metal, and may be coated with zinc, cadmium or other metals, and the nuts or fasteners may be ferrous metal, white metal, aluminum, etc., and they also may be coated with zinc, cadmium or other metals.

When the molding, panel studs or bolts, and nuts or fasteners of the prior art are assembled they form a group of many unlike metals which in the presence of moisture, salt, acid, etc., set up electrolysis and this rapidly removes the protective coatings from the parts. This leaves the parts unprotected and direct rust and oxidation then takes place while electrolysis continues resulting in the rapid decomposition of all parts.

Automobile bodies and trim provide an aggravated example of this decomposition especially were the roads are salted in winter, where gravel roads are dust-treated with hygroscopic salt material, in salt-air at sea coasts, and in industrial areas having air-borne salts and acids. Even in the absence of these conditions, the mere presence of moisture in the presence of unlike metals causes decomposition at a rapid rate.

With the foregoing in view, it is a primary object of the invention to provide an improved nonmetallic attaching means and nonmetallic fastener means for moldings, panels, and other parts to neutralize aggravated decomposition of an attaching and fastener means and to neutralize aggravated decomposition of the panels, moldings, and other parts themselves adjacent the fastening and attaching means.

A more detailed object is to achieve the foregoing by embedding a metallic thread-engaging member in a plastic body and forming the latter with a bore smaller than the stud it is to receive so as to improve the insulating effect of the plastic.

These and other objects of the invention will become apparent by reference to the following description of the novel attachment and fastener means embodying the in- 3,285,578 Patented Nov. 22, 1965 vention taken in connection with the accompanying drawing in which:

FIGURE 1 is a cross-sectional view of a panel and molding with the attaching means and fastener means of the invent-ion securing the molding and panel together showing a cross-plate having a stud and a nut threaded on the stud.

FIG. 2 is a fragmentary cross-sectional view of the assembly shown in FIG. 1 taken on the line 22 thereof.

FIG. 3 is an enlarged plan view of the nut of FIG. 1.

FIG. 4 is a cross-sectional view of the device of FIG. 3 taken on line 4-4 thereof.

FIG. 5 is a side elevational view of a modified attaching and fastener means.

FIG. 6 is a face elevational view of the attaching means and nut fastener means seen in FIG. 5.

Referring now to the drawings wherein like numerals refer to like and corresponding parts throughout the several views, the novel attaching and fastener devices disclosed therein are preferably made of nonmetallic materials such as compositions generally known as plastics. These materials include fiberglass, thermosetting resins, and thermoplastic resins of various types, strength and characteristics. These materials are insulators rather than conductors of an electrical current. Thus in any electric situation the part formed of this material interrupts the flow of current and thus insulates the adjacent metal parts. This interrupts the electrolytic action. Also, these materials are not subject to the type of decomposition usually found in metals such as rusting of ferrous metals and the oxidation of aluminum, zinc, titanium, etc. These plastic materials also eliminate the presence of several types of unlike metals in the combination of panels, moldings, attaching means and fasteners, This reduces the potential of the association of unlike metals.

While plastic materials have found their way into industrial use on a wide scale, their use alone as nuts or other fastening means has not proven entirely successful due to the fact that they do not have sufficient resistance to shear stresses to provide sufficient strength in relatively small portions such as in threads. To overcome this limitation, metal inserts of suitable quality and shear strength have been used in conjunction with a plastic body. These inserts are constructed for cutting threads on unthreaded studs or for following threads on threaded bolt portions with suitable shear strength to provide adequate torque characteristics. In this regard, threadengaging as used herein shall include both cutting and following.

More particularly, the combination of components shown in (FIGS. 14 illustrate an example and use of the novel attaching means and fastening means of the invention. A cross-plate 30 has a stud 31 and a shoulder 32. The shoulder has an aperture or opening 33. The crossplate 30, stud 31, shoulder 32 and aperture 33 may be molded out of fiberglass, thermoplastic resin or thermosetting resin. The foregoing parts are made of relatively rigid material. An arm 34- of relatively flexible synthetic resin material is inserted in the aperture 33 of the shoulder 32 and depends therefrom. The flexibility of the arm 34 gives its spring-like characteristics. When bent from a straight position to the posit-ion seen in FIGS. 1 and 2, the flexible arm 34 is spring loaded and exerts a rotating or turning influence on the cross-plate 30 to hold it in position relative to a molding 35 which locks the crossplate 30 behind a flange 36 and a flange 37 on the molding 35. The arm 34 and cross-plate 30 or other member may be inter-connected in any suitable manner. They may be molded together if desired or mechanical securing means may be employed.

After the cross-plate 30 is secured relative to the molding 35, the stud 31 is inserted through an opening in a panel 38. In this connection, the stud 31 may have a nose 39 which is reduced in cross-section axially outwardly of the stud providing a lead portion on the stud for a self-threading nut 44. The nut has a central aperture formed 'by an interior wall of suitable or desirable shape. The nut body is made of plastic and may be any shape. One or more metal inserts 45, 45A are embedded in the nut body and their ends constitute the thread-engaging portion of the nut 44.

It will be noted that the inserts 45, 45A may be somewhat rectangular in cross-section and positioned with their lateri'al axes on an angle relative to the transverse plane of the body of the nut 44 as shown in FIG. 4. This may be considered the helix angle of the thread portion of the nut 44. The helix angle of the nut therefore may be established by the inclination of the side-to-side axes of the metal inserts.

In accordance with the present invention, the insulating action of the nut is improved by forming the bore of the nut with a smaller diameter than the major diameter of the stud 31, the major diameter being the actual diameter of an unthreaded stud or the largest diameter of a threaded stud. Thus, as the stud is threaded into the bore, the latter expands and, thereafter, the wall 47 grips the stud rather tightly. This protects the point of contact between the inserts 45, 45A and the stud from moisture and minimizes electrolytic action between these parts where a metal stud is used.

The metal inserts 45, 45A have parts which project radially inwardly toward the axis of the bore to engage the stud 31. The innermost edges of these inserts are spaced from the bore axis by an amount less than oneh-alf the major diameter of the stud so that these edges either engage preformed threads on the stud or cut threads on an unthreaded stud. As thus positioned, these inner edges may project inwardly for a short distance beyond the wall 47. On the other hand, these inner edges may terminate at or even short of the wall 47. In the latter case, the expansion of the bore exposes the tips of the inserts for engagement with the stud. The use of inserts 45A which are completely embedded in the plastic body permits the easy formation of the nut by a molding operation since there is no need to protect projecting ends of the insert while the nut is being molded.

If desired, the expansion of the bore of the nut 44 may be facilitated by forming one or more longitudinal grooves 47A in the wall defining said bore. Preferably, these grooves 47A are disposed between adjacent inserts and provide spaces for the flow of plastic during expansion of nut 44 so that the expansion does not depend upon deformation of essentially the entire nut body.

Instead of making the stud rigid with the plate 30, the

nut 44 may be molded integrally with the plate 30' as shown in FIGS. 5 and 6. In such a case, the nut mates with a separate stud (not shown) which completes the fastening combination. In all other respects, the construction is the same as indicated by the same but primed reference characters.

I claim as my invention:

1. A nut adapted for use with a stud having a predetermined major diameter, said nut comprising a body of synthetic resinous plastic material having a bore defined by an internal cylindrical wall, the diameter of said bore being less than said major diameter of said stud, and a plurality of separate, straight metal inserts within the body of said nut circumferentially and axially spaced therein and each extending in a generally radial direction with respect to the axis of said internal cylindrical wall, each of said inserts having a thread-engaging inner end portion positioned adjacent said internal cylindrical wall and being spaced from said axis by a distance equal to less than one-half said major diameter of said stud but, by a distance at least equal to the spacing of said internal wall from said axis, the inner end position of each insert being formed as a cutting edge whereby said internal wall defining said bore expands as the stud is threaded into said bore and said inner end of each insert cuts a thread on the stud, the said inner ends of said inserts being generally rectangular in transverse cross section and being positioned with their lateral axes inclined relative to the transverse plane of the body of said nut, the lateral axes of said inserts being disposed along a common helix along the internal cylindrical wall defining the bore of the nut.

2. A nut as defined in claim 1 wherein each insert is completely embedded within the plastic body of the nut with the inner end of certain of said inserts being oppositely disposed and normally positioned flush with the surface of said internal cylindrical wall, expansion of said nut when being applied to said stud exposing said inner end of each insert to permit engagement thereof with said stud.

References Cited by the Examiner UNITED STATES PATENTS 88,886 4/1869 Mason 32 2,344,423 3/1944 Simmons 8536 2,393,323 1/1946 Hungerford et al 151-7 2,561,036 7/1951 Sodders 85-36 2,573,498 10/1951 Scott 85-82 2,904,820 9/1959 Flora 151-7 CARL W. TOMLIN, Primary Examiner.

EDWARD C. ALLEN, Examiner.

R. S. BRITTS, Assistant Examiner. 

1. A NUT ADAPTED FOR USE WITH A STUD HAVING A PREDETERMINED MAJOR DIAMETER, SAID NUT COMPRISING A BODY OF SYNTHETIC RESINOUS PLASTIC MATERIAL HAVING A BORE DEFINED BY AN INTERNAL CYLINDRICAL WALL, THE DIAMETER OF SAID BORE BEING LESS THAN SAID MAJOR DIAMETER OF SAID STUD, AND A PLURALITY OF SEPARATE, STRAIGHT METAL INSERTS WITHIN THE BODY OF SAID NUT CIRCUMFERENTIALLY AND AXIALLY SPACED THEREIN AND EACH EXTENDING IN A GENERALLY RADIAL DIRECTION WITH RESPECT TO THE AXIS OF SAID INTERNAL CYLINDRICAL WALL, EACH OF SAID INSERTS HAVING A THREAD-ENGAGING INNER END PORTION POSITIONED ADJACENT SAID INTERNAL CYLINDRICAL WALL AND BEING SPACED FROM SAID AXIS BY A DISTANCE EQUAL TO LESS THAN ONE-HALF SAID MAJOR DIAMETER OF SAID STUD BUT, BY A DISTANCE AT LEAST EQUAL TO THE SPACING OF SAID INTERNAL WALL FROM SAID AXIS, THE INNER END POSITION OF EACH INSERT BEING FORMED AS A CUTTING EDGE WHEREBY SAID INTERNAL WALL DEFINING SAID BORE EXPANDS AS THE STUD IS THREADED INTO SAID BORE AND SAID INNER ENDS OF EACH INSERT CUTS A THREAD ON THE STUD, THE SAID INNER ENDS OF SAID INSERTS BEING GENERALLY RECTANGULAR IN TRANSVERSE CROSS SECTION AND BEING POSITIONED WITH THEIR LATERAL AXES INCLINED RELATIVE TO THE TRANSVERSE PLANE OF THE BODY OF SAID NUT, THE LATERAL AXES OF SAID INSERTS BEING DISPOSED ALONG A COMMON HELIX ALONG THE INTERNAL CYLINDRICAL WALL DEFINING THE BORE OF THE NUT. 